fix: NavigationTree updates from testing

[snowystinger]

Closes

Fixes from testing:

• add starter storybook stories
• add test for opening a non-href item that contains children
  • as a result of this, add property to context so that we can open on a link click and not rely on the the events which were stopped by the link that wasn't doing anything
• move inline alert down to content
• fix page auto scroll, page will no longer scroll down to the last example in the navigation tree docs page
• make indicator smaller and no longer change selected one's colour on hover
• change structure of starters to support adding buttons as children
• fix webkit tap highlight

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices
• I understand every change in this PR and can explain why it's there.
• If AI-assisted, I followed our AI contribution guidance and pointed my assistant at CLAUDE.md.

📝 Test Instructions:

🧢 Your Project:

[rspbot]

Build successful! 🎉

• View the storybook
• View the S2 storybook
• View the S2 docs
• View the React Aria docs

[rspbot]

Build successful! 🎉

• View the storybook
• View the S2 storybook
• View the S2 docs
• View the React Aria docs

[rspbot]

Build successful! 🎉

• View the storybook
• View the S2 storybook
• View the S2 docs
• View the React Aria docs

[rspbot]

Agent Skills Changes

Modified (10)

• react-aria/agent-skills/index.json $\color{green}{+1}$ $\color{red}{-1}$
• react-aria/agent-skills/react-aria.tar.gz
• react-aria/agent-skills/react-aria/references/components/NavigationTree.md $\color{green}{+240}$ $\color{red}{-128}$
• react-aria/agent-skills/react-aria/references/components/Separator/useSeparator.md $\color{green}{+1}$ $\color{red}{-1}$
• s2/agent-skills/index.json $\color{green}{+3}$ $\color{red}{-3}$
• s2/agent-skills/migrate-react-spectrum-v3-to-s2.tar.gz
• s2/agent-skills/react-spectrum-s2.tar.gz
• s2/agent-skills/react-spectrum-s2/references/react-aria/components/NavigationTree.md $\color{green}{+240}$ $\color{red}{-128}$
• s2/agent-skills/react-spectrum-s2/references/react-aria/components/Separator/useSeparator.md $\color{green}{+1}$ $\color{red}{-1}$
• s2/agent-skills/spectrum-audit.tar.gz

Install

React Spectrum S2:

npx skills add https://d1pzu54gtk2aed.cloudfront.net/pr/90448eba71124d35dce34b1c96465269407912f1/

React Aria:

npx skills add https://d5iwopk28bdhl.cloudfront.net/pr/90448eba71124d35dce34b1c96465269407912f1/